This invention relates to systems and methods for monitoring parameters and for remote data telemetry. The invention also relates to radio frequency identification devices.
Electronic identification devices, such as radio frequency identification devices (RFIDs), are known in the art. Such devices are typically used for inventory tracking. As large numbers of objects are moved in inventory, product manufacturing, and merchandising operations, there is a continuous challenge to accurately monitor the location and flow of objects. Additionally, there is a continuing goal to determine the location of objects in an inexpensive and streamlined manner. One way of tracking objects is with an electronic identification system.
One presently available electronic identification system utilizes a magnetic coupling system. In some cases, an identification device may be provided with a unique identification code in order to distinguish between a number of different devices. Typically, the devices are entirely passive (have no power supply), which results in a small and portable package. However, such identification systems are only capable of operation over a relatively short range, limited by the size of a magnetic field used to supply power to the devices and to communicate with the devices.
Another type of wireless electronic identification system is an active wireless electronic identification system. Attention is directed towards commonly assigned U.S. patent application Ser. No. 08/705,043, filed Aug. 29, 1996, and incorporated herein by reference, which describes such active systems in detail. One such system is sold by Micron Communications Inc., 3176 S. Denver Way, Boise, Id. 83705 under the trademark Microstamp Engine (TM). These systems include integrated circuit devices which include an active transponder and are intended to be affixed to an object to be monitored. The devices are capable of receiving and processing instructions transmitted by an interrogator. A device receives the instruction, if within range, then processes the instruction and transmits a response, if appropriate. The interrogation signal and the responsive signal are typically radio-frequency (RF) signals produced by an RF transmitter circuit. Because active devices have their own power sources, and do not need to be in close proximity to an interrogator or reader to receive power via magnetic coupling. Therefore, active transponder devices tend to be more suitable for applications requiring tracking of a tagged device that may not be in close proximity to an interrogator. For example, active transponder devices tend to be more suitable for inventory control or tracking.
Because the Microstamp Engine (TM) is capable of communications, it can be used for applications other than just inventory tracking and other typical RFID applications.
The invention provides a wireless identification device configured to provide a signal to identify the device in response to an interrogation signal. In addition, one aspect of the invention provides coupling a digital to analog converter to the wireless identification device.
The invention also provides a communications system comprising a radio frequency identification device including an integrated circuit and method for converting a digital signal to an analog signal. The integrated circuit has a single die including a microprocessor, a receiver coupled to the microprocessor, a backscatter transmitter, and a digital output coupled to the microprocessor. The receiver is configured to receive wireless communications from a remote interrogator. The communications system further includes a digital to analog converter external of the single die. The digital to analog converter has a digital input coupled to the digital output of the integrated circuit, and has an analog output configured to be coupled to a remote analog device that utilizes a DC voltage input; e.g., for machine control circuitry, motion control circuitry, biasing of input switches, pre-scaling of window comparators, or for any other analog device that utilizes a DC voltage input.